Meteorology- Key Ideas

Atmosphere- the layer that surrounds the Earth- mixture of chemical elements that we call air-It protects the earth from the sun and regulates temperature.Atmosphere is made up mostly of Nitrogen, Oxygen and Argon. It’s origin was probably the gases that vented by erupting volcanoes. This is called outgassing.Today the atmosphere is mostly made of nitrogen and oxygen. Then, the carbon dioxide that was released was absorbed by the oceans and provided a way for organisms to use photosynthesis and produce oxygen.Nitogen is 78% of the atmosphere. The Nitrogen Cycle means it starts in air, bacteria bring it to soil, plants and animals eat it, it returns to the soil as waste, when it decays it returns to the air and the cycle starts again.Oxygen is 21% of atmosphere. It is used by natural processes and returned to the air by photosynthesis.Water Vapor- Evaporation from lakes and oceansPlants and animals give off with transpiration. Vapor then enters Atmosphere and returns to earth by condensation and precipitation.

The modern atmosphere is a result of billions of years of biological processes.

Ozone- a form of oxygen. Not O2 but O3. It is a layer in the upper atmosphere that absorbs ultra violet radiation. Emissions from machines (NO2) cause ozone to break down.The atmosphere also contains particles like dust, pollen, microscopic organisms, or even salt particles that are left when drops of ocean water are tossed into the air and vaporize. Large particles eventually settle, but tiny particles might be suspended for a long time.

Atmospheric Pressure- the force that is exerted on the surface by the weight of the atmosphere. Gravity holds the atmospheric gasses together, but temperature heats or cools the water vapor in the atmosphere, making it lighter or heavier. When temp is high, the particles are spread apart and we have less pressure.Barometer measures pressure. A low reading means that there is low pressure or usually associated with dense air. A high reading is less dense air.Air Pressure is the weight of the atmosphere. It decreases with altitude. Barometers are used to measure the weight of the atmosphere. It’s the density of the air.

As you travel up in altitude, air density decreasesBecause there is less of the atmosphere pushing down.

As temperature goes down, so does air density.

As humidity increases, atmospheric pressure decreases.

Moisture makes the air less dense because it replaces Nitrogen in air and it is lighter.

Atmosphere Layers- Troposhere- closest to earth- most carbon dioxide and water vapor. Contains most of the atmospheres mass. This is where weather takes place. As we go higher, the temp decreases.The stratosphere- Next layer up. At it’s highest it is the Ozone (which absorbs the suns heat) so as you go higher, the temperature increases. The Mesosphere- Next layer up (above stratosphere) as you go higher the temp goes way down. Thermosphere is the top layer- As altitude increases so does temperature. Here the nitrogen and oxygen atoms absorb solar radiation and produce temperatures of over 1000 degrees. We call the lower part of the thermosphere the ionosphere because the atoms loose electrons and become ions

Upper boundaries of these layers have names that end in –pause… tropopause, stratopause.

Weather is the condition in the atmosphere at a given place and time. The study of weather is called meteorology.

Climate describes the long-term pattern of weather at a given location. Climate is described by temperature and precipitation. Latitude is the major influence over climateWeather and climate are key components of Earth's energy flow and cycles of matter, especially water, oxygen and carbon dioxide.

2 cycles control weather- daily weather cycle and seasons

Energy can be transferred three ways:

Radiation travels as electromagnetic waves and can even pass through empty space.

Radiant energy encountering a substance may be transmitted, absorbed, reflected, or refracted. Dark-colored objects are good absorbers and radiators of heat, and poor reflectors. Light-colored objects are good reflectors, but poor absorbers or radiators.Smooth surfaces are good reflectors and dark surfaces are good absorbers.Kinetic energy is energy of moving things. The faster they move, the more KE they use.Temperature is the "average kinetic energy" of an object. Potential energy is stored energy. It increases with mass and as the object gets higher.Radiative balance (equilibrium) occur when the energy emitted by an object is equal to that absorbed by the object.The amount of insolation reaching Earth is balanced by the amount reflected back to space (albedo) and the terrestrial re-radiation, mostly as infrared waves.

The Greenhouse effect- the warming of the surface and lower atmosphere that occurs when carbon dioxide, water vapor and other gases in the air absorb and then reflect or radiate back toward the lower atmosphere and then back to earth’s surface

Important weather variables include: air temperature, air pressure, wind direction, wind speed, relative humidity, dew point, clouds, and precipitation. Air temperature is measured with a thermometer in degrees (Celsius/centigrade or Fahrenheit). (ESRT p. 13)Air pressure is measured with a barometer in millibars or inches of mercury. (ESRT p. 13)

Latent Heat- the energy absorbed and released during a phase change. (Ice/snow, melts, evaporates)

Sublimation- When a solid (ice) turns into gas (vapor) without first becoming liquid (usually only when air is dry)

Dew point temperature is the temperature to which air must be cooled to reach saturation, at which drops of dew will form. If the dew point temperature is below freezing, frost crystals will form. The rate of condensation equals the rate of evaporation

Problems that deal with dew point and relative humidity can be solved by using the ESRT p 12 REMEMBER that we deal with the difference between web and dry bulb temperatures, so find the difference by subtracting one from the other and then use the chart.

Absolute Humidity- the mass of water vapor per volume of air

Relative humidity is a measure of how much water vapor is contained in the air compared with how much it could hold at that temperature. When air holds all the moisture is can, it is said to be at 100% relative humidity and saturated.

Psychrometers made of wet- and dry-bulb thermometers measure relative humidity and dew point. As temperature of the air approaches dew point, the relative humidity approaches 100%

The only way to change the dew point is by adding or removing moisture from the air.

Clouds are collections of small water droplets or ice crystals suspended in the air.

Clouds reduce daytime temperature by reflecting sunlight into space and hold temperatures at night by holding heat energy on earth.

Clouds will form when air cools and saturation occurs above the surface. Water or ice attach to invisible condensation. The suspended particles in the atmosphere provide the surface for the condensation to gather. This is the condensation nuclei

Meteorologists measure the amount of cloud cover.

Clouds can be classified into three basic shapes: stratus (flat) gray forms in low altitudes, cumulus (fluffy)can have a dark bottom, and cirrus (feathery)ice crystals , highest altitude. The term "nimbo" is used to indicate a storm cloud, as in nimbostratus or cumulonimbus.

Precipitation includes all forms of water coming out of the atmosphere, and includes rain, snow, sleet, hail, and drizzle. Precipitation typically occurs along and ahead of the warm front and along and behind a cold front and around the center of a low pressure system

Coalescence- the formation of large droplets by combination of smaller dropletsSupercooling- a condition in which a substance is cooled below its freezing point without going through a change in state. Rain and snow in high latitude areas form ice as a result of supercooling.

Precipitation cleans the air of pollution by washing dust and other air-borne particulates.

Fog- water vapor that has condensed very near the surface of the Earth because air close to the ground has cooled.

Weather at a location can be symbolically represented by a station model. (ESRT p. 13)

We measure precipitation with Doppler Radar- Bouncing radio waves off of rain and snow

Cloud seeding is the process of introducing condensation nuclei into a cloud to cause rain to fall

Many weather variables exhibit relationships with each other.

As air temperature increases, air pressure decreases (inverse relationship).

As altitude increases the atmospheric pressure will decreases.

As air humidity increases, air pressure decreases (inverse relationship). This occurs because water molecules, which have less mass, displace heavier nitrogen and oxygen molecules as humidity increases.Modern weather observation systems also use weather radar, weather satellites, and other instrument systems, such as radiosondes sent aloft on weather balloons.Wind is heat flow by way of convection inside the atmosphere.

Wind speeds can be found on a weather map by looking at the gradient of the isobars. They are at their greatest where the isobars are closest together.

Wind is measured in both direction and magnitude (vector).

Wind direction is measured with a wind vane. Winds are named by the direction they blow from.Wind speed (velocity) is measured with an anemometer. Units used include miles per hour, km/hr, and knots (nautical miles per hour.)

Global and Regional Weather and Climate SystemsLocal weather is a small part of global and regional weather patterns.Global wind, pressure, and precipitation patterns result from differences in the amount of energy received at different latitudes and Earth's rotation.

The Coriolis effect is the curving of the path of a moving object from a straight motion due to the Earth’s Rotation. If the earth was not turning the wind would blow straight from the poles to the equator, but because it is spinning, the winds move. This causes winds in the northern hemisphere to turn to the right of their direction of movement, and winds in the southern hemisphere to turn to their left. This produces clockwise patterns in the northern hemisphere and counterclockwise patterns in the southern hemisphere.

Trade Winds blow east to west from 30 degrees latitude to the equator in both hemispheresWesterlies blow west to east between 30 and 60 degrees latitude in both hemispheresPolar Easterlies blow from east to west from 60 – 90 latitude in both hemispheres.

Global climate patterns (ESRT p. 14) include: wet conditions and calm winds centered around the equator (doldrums); east-to-west winds trade winds in the tropics; zones of calm centered around 30 degrees north and south ("horse latitudes"); west-to-east winds in the mid-latitudes ("prevailing westerly"); and east-to-west winds at high latitudes ("polar easterlies").Wind blows from areas of higher pressure to areas of lower pressure.

The stronger the pressure gradient (difference from one location to another), the faster the wind speed.

Jet Stream- is a narrow band of strong winds that blow in the upper troposphere.

Regional weather (on the scale of several states) results from the movement of air masses, weather fronts, and pressure systems.

In the United States, most weather systems move from west to east under the influence of the prevailing westerly.

Air Mass- a large body of air throughout which temperature and moisture are similar Continental air mass- dry and formed over land. Maritime Air mass- moist- high humidity form over large bodies of water Tropical air mass- bring hot and humid (thunderstorms) Polar- From the poles – bring cold and dry air inAir masses are large bodies of air that display similar temperature and moisture characteristics. They are named after the type of geography over which they form.Continental Polar (cP) air masses are generally dry and cool/cold. They form over central Canada and move southeastward across the United States.

Continental Tropical (cT) air masses are dry and warm/hot. They form over Mexico and the Southwest. Maritime Polar (mP) air masses are humid and cool. They mostly affect weather in the Pacific Northwest and New England.Maritime Tropical (mT) air masses are humid and warm. They may form over the Gulf of Mexico and move northeastward across the U.S.Weather predictions are based largely on air mass movements.

When air masses meet, their boundaries are weather fronts.

A cold front occurs when cooler air (such as cP) moves faster than warmer air (such as mT.) The warmer air is forced upward. Cold fronts often bring a brief period of heavy rain or even thunderstorms, followed by rapid clearing and cooler temperatures. On a weather map, cold fronts are indicated by triangles pointing in the direction the front moves.

A warm front occurs when a warmer air mass pushes colder air ahead of it. Warm fronts extend over a much wider region than cold fronts. Cirrus clouds at the leading edge of the front may be seen a day or two before the front arrives. As the front passes, there may be steady rain, then gradual clearing and warming. Half-circles indicate a warm front on a weather map.

High temperatures can be found behind a warm front and ahead of a cold front

A stationary front develops when neither air mass can move the other. Weather is usually cloudy with occasional showers. It is represented on a weather map by triangles and half-circles on opposite sides of the line.

An occluded front forms when a second cold air mass overtakes a warm front and lifts it above the ground. Weather is similar to that in a warm front. The map symbol involves triangles and half-circles on the same side of the line.Movements of air masses and fronts are also influenced by large-scale pressure systems.

Cyclones are low-pressure systems that usually bring unsettled weather. Air circulates counterclockwise and inward to the center of the cyclone. Many cyclones are associated with cold and occluded fronts.

Anticyclones are high-pressure systems that often occur within an air mass They generally bring fair weather. Air circulates outward in a clockwise direction around an anticyclone. (Note: In the southern hemisphere, high circulate in a counterclockwise direction and lows in a clockwise direction.)

If the barometric pressure is rapidly falling it probably means a storm is approaching. Rising air pressure often indicates fair weather will follow.

Thunderstorm- usually brief, heavy storm with wind, rain, thunder and lightning. Lightning is the discharge of electricity or energy from the clouds. The heat of the lightning heats the air forcing it to expand rapidly and a noise called thunder is produced.

Hurricane- a sever storm that develops over tropical oceans with strong winds over 120km/hr that spiral in toward the intensely low pressure center.

Tornado- a destructive rotating column of air that has very high wind speeds that maybe visible as a funnel-shaped cloud. It occurs when a thunderstorm meets high altitude horizontal winds.

Additional Climate and Weather FactorsAdiabatic Cooling: As air rises, it cools because it expands and the pressure decreases.Adiabatic Heating: As air sinks, it warms as it contracts and the pressure increases.

Orographic effect: As air rises up the windward side of a mountain, adiabatic cooling occurs, and as it sinks down the leeward side, adiabatic warming occurs. So the windward side has greater cloud cover and precipitation, and the leeward side often has a rain-shadow desert.

El Nino is a changing wind or water current problem in the Pacific Ocean.

Monsoons are seasonal winds that blow toward the land in the summer bringing heavy rains. They blow away from land in the winter bringing dry weather.

Water has a higher specific heat value than minerals and rocks, so when the same amount of insolation strikes materials at a shoreline, the water will remain cooler and the beach will warm up more rapidly. These heating rate differences produce on-shore sea breezes during the day and off-shore land breezes at night.Large bodies of water make cooler summers and warmer winters.

On a regional scale, similar factors create the monsoons, with wet-seasons in summer and dry-seasons in winter.

Because warming and cooling take time, generally the hottest part of the day occurs in mid-afternoon, even though insolation is greatest at solar noon. Similarly, the warmest days of the year usually occur in July or August, even though maximum insolation occurs in late June, and the coldest days are in January or February, even though insolation minimum values occur in late December. These patterns are called "temperature lags". Without certain atmospheric gases that absorb infrared energy in terrestrial re-radiation, Earth would have a frozen surface, given its distance from the Sun. These greenhouse gases include carbon dioxide, water vapor, and methane.

There is increasing evidence that human releases of carbon dioxide and other greenhouses gases has contributed greatly to global warming during the past few decades, which will have significant impact on climate systems in the next few decades. Possible effects include stronger hurricanes and rising sea level, which will especially affect coastal regions.

ToolsThermometer is used to measure temperatureBarometers measure air pressurePsychrometer meatures relative humidityAnemometers measure wind speedWind vane tells the direction of the windRadar stands for Radio detection and ranging system- it Determines the velocity and location of objects